Automatic adjustment devices which allow to have a single ring which may be worn on fingers different in circumference are known.
For example, U.S. Pat. No. 6,748,764 describes a ring comprising a circular structure which defines an internal cavity which accommodates one or more springs. Such springs act against one or more arms hinged to the structure, so as to rotate the arms towards the interior of the ring against the finger on which the ring is worn. In such a manner, the position of the arms with respect to the centre of the ring may be automatically adapted according to the size of the finger on which the ring is worn.
The known solutions shown in U.S. Pat. No. 6,748,764 are poorly satisfactory, because the type of springs and the mode for assembling the springs into the structure of the ring require internal cavities having relatively large dimensions in the radial direction.
Furthermore, at least in some known solutions disclosed in U.S. Pat. No. 6,748,764, the springs have no fixed position in the internal cavity of the whereby they could move in use, with the consequent risk of preventing or limiting the automatic adaptation of the arm position.